Filament lamp with reflector

ABSTRACT

The invention provides a lighting device (10) comprising (i) a plurality of elongated filaments (100) and (ii) an optical element (200), wherein: —each elongated filament (100) comprises a support (105) and a plurality of solid state light sources (110), wherein the elongated filament (100) has a first axis of elongation (120) having a first length (L1), wherein the elongated filament (100) is configured to generate filament light (101) over at least part of the first length (L1); and—the optical element (200) comprises a plurality of facets (210), wherein the optical element (200) has a second axis of elongation (220) having a second length (L2), wherein the optical element (200) has a non-circular cross-section perpendicular to the second axis of elongation (220), wherein the optical element (200) is configured between at least two of the plurality of elongated filaments (100), and wherein the optical element (200) is configured to redirect at least part of the filament light (101).

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is the U.S. National Phase application under 35 U.S.C.§ 371 of International Application No. PCT/EP2020/054142, filed on Feb.18, 2020, which claims the benefit of European Patent Application No.19159892.9, filed on Feb. 28, 2019. These applications are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a lighting device.

BACKGROUND OF THE INVENTION

Filament-type of lighting devices are known in the art. U.S. Pat. No.8,400,051 B2, for instance, describes a light-emitting devicecomprising: an elongated bar-shaped package with left and right ends,the package being formed such that a plurality of leads are formedintegrally with a first resin with part of the leads exposed; alight-emitting element that is fixed onto at least one of the leads andthat is electrically connected to at least one of the leads; and asecond resin sealing the light-emitting element, wherein the leads areformed of metal, an entire bottom surface of the light-emitting elementis covered with at least one of the leads, an entire bottom surface ofthe package is covered with the first resin, the first resin has a sidewall that is integrally formed with a portion covering the bottomsurface of the package and that is higher than upper surfaces of theleads, the first resin and the second resin are formed of opticallytransparent resin, the second resin that is filled to a top of the sidewall of the first resin and that includes a fluorescent material havinga larger specific gravity than that of the second resin, the leads haveouter lead portions that are used for external connection and thatprotrude in a longitudinal direction of the package from the left andright ends wherein the fluorescent material is arranged to concentratenear the light emitting element, and is excited by part of light emittedby the light-emitting element so as to emit a color different from acolor of the light emitted by the light-emitting element, and the sidewall transmits part of light that is emitted by the light-emittingelement and that enters the side wall and part of light emitted from thefluorescent material to the portion covering the bottom surface of thepackage.

US2013/286664A1 discloses a LED light bulb capable of providing evenluminous intensity distribution. The LED light bulb includes a base, alight transmissive cover and upstanding light bars. The lighttransmissive cover is substantially mounted on the periphery. The lightbars are positioned around a reflector and emit light towards thereflector. The reflector has curved side wall that reflects the lightfrom the light bars.

EP2827046A1 discloses a LED lamp with a LED light-emitting column thatcomprises a high thermal conductivity tube and at least one series ofLED chips disposed on an outer surface of the high thermal conductivitytube. The LED light comprises a light-transmitting bulb shell filledwith a heat dissipation and protection gas, a LED driver and anelectrical connector. The LED light-emitting column is fixed within thebulb shell.

SUMMARY OF THE INVENTION

Incandescent lamps are rapidly being replaced by LED based lightingsolutions. It may nevertheless be appreciated and desired by users tohave retrofit lamps which have the look of an incandescent bulb. Forthis purpose, one may make use of the infrastructure for producingincandescent lamps based on glass and replace the filament with LEDsemitting white light. One of the concepts is based on LED filamentsplaced in such a bulb. The appearances of these lamps are highlyappreciated as they look highly decorative.

However, known solutions may not have a sufficient uniformomnidirectional light distribution.

It appears that depending on the targeted application, either thebrightness of the filaments may be too high and/or the appearance of thebulb may be too static or is lacking appeal. Applying a diffusing outerbulb may reduce the brightness but may also reduce efficiency.

It appears that for an increased appeal of the lamp appearance multiplefilament segments might be used. However, these may be more difficult toimplement and it may be expensive to manufacture and assemble. Foradjustments of the beam profile an integrated reflector may be applied,but this may not contribute to a higher appeal factor, such as a sparkleeffect, and may limit the beam to a smaller beam angle.

Hence, it is an aspect of the invention to provide an alternativelighting device, which preferably further at least partly obviates oneor more of above-described drawbacks. The present invention may have asobject to overcome or ameliorate at least one of the disadvantages ofthe prior art, or to provide a useful alternative.

Amongst others, a LED lamp comprising one or more, especially aplurality, such as at least three, LED filaments adapted for, inoperation, emitting LED filament light is herein suggested. Inembodiments, a LED filament comprises a linear array of LEDs on anelongated substrate (or support), especially encapsulated by aluminescent material comprising material. The LED filament(s) may bearranged in an at least partly transparent envelope. The light emittingsurface of the LED filament(s) are especially oriented towards adistantly arranged reflective (or refractive) element which is centrallyarranged in the envelope. In embodiments, the LED filaments are evenlyarranged around the reflective element. The reflective element may inembodiments have reflective surfaces for reflecting light in otherdirections, especially for obtaining omnidirectional distribution. Inembodiments, the reflective element may be cone-shaped. In specificembodiments, the reflective element may have a double cone shape (twocone configuration). For instance, in specific embodiments thereflective element may have a double pyramid shape (two pyramidconfiguration). The surface area of the top pyramid may in embodimentsbe larger than the surface area of the bottom pyramid. In furtherspecific embodiments, the LED filament may be chosen to emit light fromonly one surface facing the reflector, such as for preventing glare. Theother surface may be covered by a layer (other than a phosphor), e.g. ablack/metal coating, for instance to give the filament the appearance ofan incandescent lamp. Hence, amongst others (also) a segmented reflectorin the center of the lamp is herein suggested, with the filament(s)mounted around this reflector. In embodiments, this reflector may alsoact as support for the filaments and may enable feedthrough of thecurrent conductor(s) from the top end of the filaments back to thedriver or socket. By segmentation of the central reflector, multiplepartial images of the filaments may become visible depending on thenumber of facets, their orientation, and the number and position of thefilaments. By the segmentation, dynamic sparkle effects may be createdas one looks at a lamp with virtual source brightness distributions thatchange with varying viewing position. These effects may be more or lesspronounced related to the shape and size of the reflector segments(flat, concave, convex, orientation of the normal of the reflectorsegment relative to the filaments).

Hence, in an aspect the invention provides a lighting device comprising(i) one or more (elongated) filaments, especially a plurality of(elongated) filaments and (ii) an optical element (herein also indicatedas “reflector”), wherein:

one or more of the, especially each, of the (elongated) filament (orfilament light source) comprises a support and a plurality of solidstate light sources, wherein the (elongated) filament may in embodimentshave a first axis of elongation having a first length (L1), wherein the(elongated) filament is configured to generate filament light,especially over at least part of the first length (L1); and

the optical element comprises a plurality of facets, wherein the opticalelement may have a second axis of elongation having a second length(L2), wherein in specific embodiments the optical element has anon-circular cross-section perpendicular to the second axis ofelongation, wherein in further specific embodiments the optical elementis configured between at least two of the plurality of (elongated)filaments, and wherein the optical element is configured to redirect atleast part of the filament light.

The solid state light sources are arranged to generate solid state lightsource light. With such lighting device it may be possible to create amore omnidirectional distribution of the light. Alternatively oradditionally, with such lighting device also lighting effects may becreated, such as sparkle effects.

Sparkle effects may also be indicated as “pleasant glare”. Theboundaries between bright, glaring and sparkling luminous elements maydepend on the luminance and solid angle (angular extent of the brightelement with respect to the eye of the observer, or A/R², where A is theprojected area of the element as seen by the observer, and R is theobserver distance).

As indicated above, the invention provides (amongst others) a lightingdevice comprising (i) one or more filaments, especially a plurality ofelongated filaments and (ii) an optical element.

Herein, the term “filament” may refer to support and a plurality ofsolid state light sources supported by the support and that may bearranged in a linear array. The filament may especially comprise a 1Darray of solid state light sources. A 2D array of light solid statelight sources may also be possible, though especially with the number ofrows (n1) much smaller than the number (n2) of solid state light sourcesin the respective rows, such as n1/n2≤0.2, like n1/n2≤0.1, especiallyn1/n2≤0.05. In specific embodiments, the support supports a (1D) arrayof solid state light sources at one side of the support, and optionallyanother (1D) array of solid state light sources at the other side of thesupport. Preferably, the filament has a length L and a width W, whereinL>5W. The filament may be arranged in a straight configuration or in anon-straight configuration such as for example a curved configuration, a2D/3D spiral or a helix. Preferably, the solid state light sources arearranged on an elongated carrier like for instance a substrate, that maybe rigid (made from e.g. a polymer, glass, quartz, metal or sapphire) orflexible (e.g. made of a polymer or metal e.g. a film or foil). In casethe carrier comprises a first major surface and an opposite second majorsurface, the solid state light sources are arranged on at least one ofthese surfaces. The carrier may be reflective or light transmissive,such as translucent and preferably transparent. The filament maycomprise an encapsulant at least partly covering at least part of theplurality of solid state light sources. The encapsulant may also atleast partly cover at least one of the first major or second majorsurface. The encapsulant may be a polymer material which may be flexiblesuch as for example a silicone. Further, the solid state light sourcesmay be arranged for emitting solid state light source light e.g. ofdifferent colors or spectrums. The encapsulant may comprise aluminescent material that is configured to at least partly convert solidstate light source light into converted light. The luminescent materialmay be a phosphor such as an inorganic phosphor and/or quantum dots orrods. The filament may comprise multiple sub-filaments.

The support may in embodiments have a thickness of 0.05-4 mm, such as0.05-1 mm, like 0.1-0.5 mm. The support may have a width of 0.1-5 mm,such as 0.2-3 mm, like 0.3-2 mm. The length of the support (and thus inembodiments essentially the length of the filament), herein alsoindicated as first length (L1), may in embodiments e.g. be selected fromthe range of 10-500 mm, such as 15-200 mm, like in the range of 20-100mm, such as in the range of 25-80 mm, for example 40 or 50 mm. Hence,the support (and thus essentially also the filament) may have relativehigh aspect ratios (length/width or length/thickness), such as at least10, even more especially at least 15, such as at least 20, like evenmore especially at least 50. Large aspect ratios may better mimic afilament.

The support may e.g. comprise glass or sapphire. In other embodiments,the support may comprise a polymeric material. As also indicated below,the support may be rigid (self-supporting), but may (in polymericembodiments) also be flexible. The first length is especially the lengthalong the axis of elongation.

In embodiments, the support may be translucent. In other embodiment, thesupport may be transparent. Hence, the material of the support may betranslucent or transparent for light, especially visible light. Fortransparent materials, see also below.

The elongated filament may have a straight axis of elongation, when theelongated filament is straight. However, the elongated filament mayalso—in embodiments—include a plurality of segments, of which two ormore may be configured under an angle 180°; ≠0°) relative to oneanother. Alternatively or additionally, the elongated filament mayinclude one or more curvatures, for instance a curved segment, or twosegments that are configured under an angle and which are connected viaa curved segment. Hence, in embodiments the axis of elongation may alsoinclude one or more curvatures and/or one or filament segments that areconfigured under an angle (≠180°) relative to one another. Hence, thefilament may comprise a single segment, or may comprise a plurality ofsegments (with each segment comprising one or more solid state lightsources). Especially, herein the elongated filaments are essentiallystraight filaments. The one or more filaments may in embodiments beself-supporting (straight) filaments (see also above).

The term “light source” may refer to a semiconductor light-emittingdevice, such as a light emitting diode (LEDs), a resonant cavity lightemitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edgeemitting laser, etc. The term “light source” may also refer to anorganic light-emitting diode, such as a passive-matrix (PMOLED), or anactive-matrix (AMOLED). In specific embodiments, the light sourcecomprises a solid state light source (such as a LED or laser diode). Inembodiments, the light source comprises a LED (light emitting diode).The term “LED” may also refer to a plurality of LEDs. Further, the term“light source” may in embodiments also refer to a so-calledchips-on-board (COB) light source. The term “COB” especially refers toLED chips in the form of a semiconductor chip that is neither encasednor connected but directly mounted onto a substrate, such as a PCB.Hence, a plurality of semiconductor light sources may be configured onthe same substrate. In embodiments, a COB is a multi LED chip configuredtogether as a single lighting module. The term “light source” may alsorelate to a plurality of (essentially identical (or different)) lightsources, such as 2-2000 solid state light sources. In embodiments, thelight source may comprise one or more micro-optical elements (array ofmicro lenses) downstream of a single solid state light source, such as aLED, or downstream of a plurality of solid state light sources (i.e.e.g. shared by multiple LEDs). In embodiments, the light source maycomprise a LED with on-chip optics. In embodiments, the light sourcecomprises a pixelated single LEDs (with or without optics) (offering inembodiments on-chip beam steering).

The phrases “different light sources” or “a plurality of different lightsources”, and similar phrases, may in embodiments refer to a pluralityof solid state light sources selected from at least two different bins.Likewise, the phrases “identical light sources” or “a plurality of samelight sources”, and similar phrases, may in embodiments refer to aplurality of solid state light sources selected from the same bin.

It may also be possible that the light source light of the solid statelight sources at one side of the support has another spectraldistribution and/or intensity than the light source light of the solidstate light sources at another side of the support (in embodimentswherein solid state light sources are available at both sides of thesupport).

Alternatively or additionally, it may be that the spectral distributionof the filament light varies along the length of the filament (at oneside or at both sides).

An example of a suitable elongated light source is described in U.S.Pat. No. 8,400,051 B2, which is herein incorporated by reference.

Hence, in embodiments the elongated light source may comprise a firstlight-emitting device comprising: an elongated bar-shaped packageextending sideways, the package being formed such that a plurality ofleads are formed integrally with a first resin with part of the leadsexposed; a light-emitting element that is fixed onto at least one of theleads and that is electrically connected to at least one of the leads;and a second resin sealing the light-emitting element, characterized inthat the first resin and the second resin are formed of opticallytransparent resin, and the leads have outer lead portions used forexternal connection and protruding sideways from both left and rightends of the package.

In yet embodiments, the elongated light source may comprise a firstlight-emitting device comprising: an elongated package being formed suchthat a plurality of leads are formed integrally with a first resin; aplurality of light-emitting elements that are fixed onto at least one ofthe leads and that are electrically connected to at least one of theleads; and an optically transparent second resin sealing thelight-emitting elements, wherein the first resin includes side wallswhich are higher than upper surfaces of the leads, and an entire lowersurface of the package is covered with the first resin; and wherein theleads are formed of a metal material and part of the leads have outerlead portions used for external connection which protrude from both endsof the package in longitudinal direction, characterized in that thefirst resin is formed of optically transparent resin.

In an embodiment, the elongated filament comprises luminescent materialconfigured to convert at least part of the solid state light sourcelight into luminescent material light and wherein the filament lightcomprises the luminescent material light and optionally solid statelight source light.

In yet other embodiments, the elongated light source may comprise afirst light-emitting device comprising: an elongated bar-shaped packagewith left and right ends, the package being formed such that a pluralityof leads are formed integrally with a first resin with part of the leadsexposed; a light-emitting element that is fixed onto at least one of theleads and that is electrically connected to at least one of the leads;and a second resin sealing the light-emitting element, wherein the leadsare formed of metal, an entire bottom surface of the light-emittingelement is covered with at least one of the leads, an entire bottomsurface of the package is covered with the first resin, the first resinhas a side wall that is integrally formed with a portion covering thebottom surface of the package and that is higher than upper surfaces ofthe leads, the first resin and the second resin are formed of opticallytransparent resin, the second resin that is filled to a top of the sidewall of the first resin and that includes a luminescent material havinga larger specific gravity than that of the second resin, the leads haveouter lead portions that are used for external connection and thatprotrude in a longitudinal direction of the package from the left andright ends wherein the luminescent material is arranged to concentratenear the light emitting element, and is excited by part of light emittedby the light-emitting element so as to emit a color different from acolor of the light emitted by the light-emitting element, and the sidewall transmits part of light that is emitted by the light-emittingelement and that enters the side wall and part of light emitted from theluminescent material to the portion covering the bottom surface of thepackage.

Further, in embodiments the second resin includes luminescent material.Especially, in embodiments the first light-emitting device may comprise:a plurality of first light-emitting devices as described above; afilament including these light-emitting devices; and power supply leadselectrically connected to the filament, wherein the filament is soconfigured that adjacent ones of outer lead portions are firmly attachedand connected in series such that adjacent ones of the light-emittingdevices are V-shaped, and both ends of the outer lead portions connectedin series are firmly attached to the power supply leads.

Such type of elongated light sources, wherein a plurality of solid statelight sources are configured on a support with a resin includingluminescent material configured around at least part of the plurality ofLEDs are known in the art as (embodiments of) LED filaments. They maygenerate white light, due to the combination of e.g. blue emitting solidstate light sources and a luminescent material, such as a ceriumcomprising garnet, that is configured to convert part of the blue lightinto yellow light, thereby providing white light. Of course, also othercombinations of light sources and luminescent materials may be chosen,such as blue solid state light source light with yellow and redluminescing luminescent material(s); blue solid state light source lightwith green and red luminescing luminescent material(s); UV solid statelight source light with blue, green and red luminescing luminescentmaterial(s). Further luminescent materials may also be applied in any ofthe suggested combinations, such as cyan and/or amber luminescentmaterials.

In embodiments, the filament may comprise a substrate (which is anembodiment of a support) having an elongated body with an extensionalong an elongation axis, a plurality of solid state light sources, suchas LEDs, mechanically coupled to the substrate, and wiring for poweringthe plurality of LEDs.

Further, also different types of solid state light sources may beapplied (optionally in embodiments at different sides of the support;see also above). For instance, the blue emitting solid state lightsources may be applied in combination with one or more of cyan lightemitting solid state light sources and amber light emitting solid statelight sources. The cyan light emitting solid state light sources andamber light emitting solid state light sources, respectively, may beobtained with using the same type of solid state light source used forgenerating the blue solid state light source light, but in combinationwith a specific luminescent material.

Therefore, in embodiments the elongated light source comprises a LEDfilament, wherein the elongated light source comprises luminescentmaterial configured to convert at least part of the solid state lightsource light into luminescent material light, wherein the light sourcelight comprises the luminescent material light and optionally solidstate light source light.

The term “luminescent material” may thus also refer to a plurality ofdifferent luminescent materials.

Hence, in general the filament light will have a spectral distributionwith a plurality of wavelengths, such as is the case with the blue lightof a blue LED or with the yellow light of a trivalent cerium comprisinggarnet based luminescent material or many Eu²⁺ based luminescentmaterial.

In embodiment, the elongated light source is configured to generatewhite light. The term white light herein, is known to the person skilledin the art. It especially relates to light having a correlated colortemperature (CCT) between about 2000 and 20000 K, especially 2700-20000K, for general lighting especially in the range of about 2700 K and 6500K, and especially within about 15 SDCM (standard deviation of colormatching) from the BBL (black body locus), especially within about 10SDCM from the BBL, even more especially within about 5 SDCM from theBBL.

In embodiments, the light source may also provide light source lighthaving a correlated color temperature (CCT) between about 5000 and 20000K, e.g. direct phosphor converted LEDs (blue light emitting diode withthin layer of phosphor for e.g. obtaining of 10000 K). Hence, in aspecific embodiment the light source is configured to provide lightsource light with a correlated color temperature in the range of5000-20000 K, even more especially in the range of 6000-20000 K, such as8000-20000 K. An advantage of the relative high color temperature may bethat there may be a relative high blue component in the light sourcelight.

Therefore, in embodiments each elongated filament comprises a supportand a plurality of solid state light sources (at one or at both sides ofthe support). The solid state light sources are especially configured togenerate solid state light source light. In embodiments, this lightsource light may at least partly be converted into luminescent materiallight by a luminescent material. Hence, the filament light generated bythe filament may comprise one or more of solid state light source lightand luminescent material light, especially in embodiments both. Notethat in embodiments the spectral distribution of the filament light mayvary over the length of the filament and/or depend upon the side of thefilament.

Hence, the elongated filament has a first axis of elongation having afirst length (L1), wherein the elongated filament is configured togenerate filament light over at least part of the first length (L1). Forinstance, over at least 70% of its length, especially at least 80% ofits length, even more especially at least 90%, such as yet even moreespecially at least 95%, such as at least 98% of its length, filamentlight may be generated. In general, over essentially the entire lengthof the filament light may be generated, such that the filament isperceived as a (classical) filament.

The solid state light sources may have a pitch selected from the rangeof 0.3-3 mm.

In specific embodiments, solid state light sources are only available atone side of the support. In such embodiments, the filament mayessentially not be a radial emitter (radial with respect to the firstaxis of elongation). In other embodiments, solid state light sources areonly available at both sides of the support. In such embodiments, thefilament may essentially be a radial emitter (radial with respect to thefirst axis of elongation).

In order to redistribute at least part of the filament light, theoptical element is provided.

In specific embodiments, the optical element may comprise a plurality offacets.

The optical element has a second axis of elongation having a secondlength (L2). When the filaments are not slanted and not curved, thelength of the first axis of elongation and the second axis of elongationmay in embodiments approximately be the same, such as 0.9≤L1/L2≤1.1.

In embodiments, each facet may have a facet area selected from the rangeof 0.5-20 cm², such as especially 1-20 cm², like more especially 1-10cm², such as in embodiments 1.5-10 cm², like in further embodiments 2-8cm². However, other dimensions may also be possible.

The phrase “a plurality of facets” may refer to a plurality of facetsalong the length of the second axis of elongation of the opticalelement. The phrase “a plurality of facets” may also refer to aplurality of facets along a dimension perpendicular to the length of thesecond axis of elongation of the optical element. For instance, acylindrical optical element may have a single facet, a cone may have asingle facet, a double cone may have two facets, a triangular pyramid(regular tetrahedron) may have three facets (assuming a bottom facetperpendicular to the second axis of elongation), and a double triangularpyramid may have six facets (assuming the bottom facets perpendicular tothe second axis of elongation), etc. etc.

Adjacent facets may have mutual facet angles (α1), which are especiallyunequal to 0° (and unequal to 180°). For instance, in the case of aregular tetrahedron, the facets may have facet angles α1=60°.

The optical element is especially configured to redirect at least partof the filament light. Hence, the optical element may have one or moreproperties selected from the group consisting of reflection, refraction,and scattering. In this way, the optical element may have reflectiveproperties.

For instance, in embodiments the optical element may comprise a lighttransparent material, and due to the presence of the facets, light mayrefract at the facets. In this way, the optical element may beconfigured to redirect at least part of the filament light (byrefraction at the facets). For instance, in embodiments visible lightpropagating in a direction perpendicular to the second axis ofelongation may meet one or more facets, configured such that visiblelight is refracted.

Hence, in specific embodiments the optical element may be a lighttransparent body essentially consisting of a light transmissive material(that is especially transparent).

The light transmissive material may comprise one or more materialsselected from the group consisting of a transmissive organic material,such as selected from the group consisting of PE (polyethylene), PP(polypropylene), PEN (polyethylene napthalate), PC (polycarbonate),polymethylacrylate (PMA), polymethylmethacrylate (PMMA) (Plexiglas orPerspex), cellulose acetate butyrate (CAB), silicone, polyvinylchloride(PVC), polyethylene terephthalate (PET), including in an embodiment(PETG) (glycol modified polyethylene terephthalate), PDMS(polydimethylsiloxane), and COC (cyclo olefin copolymer). Especially,the light transmissive material may comprise an aromatic polyester, or acopolymer thereof, such as e.g. polycarbonate (PC), poly(methyl)methacrylate (P(M)MA), polyglycolide or polyglycolic acid (PGA),polylactic acid (PLA), polycaprolactone (PCL), polyethylene adipate(PEA), polyhydroxy alkanoate (PHA), polyhydroxy butyrate (PHB),poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polyethyleneterephthalate (PET), polybutylene terephthalate (PBT), polytrimethyleneterephthalate (PTT), polyethylene naphthalate (PEN); especially, thelight transmissive material may comprise polyethylene terephthalate(PET). Hence, the light transmissive material is especially a polymericlight transmissive material. However, in another embodiment the lighttransmissive material may comprise an inorganic material. Especially,the inorganic light transmissive material may be selected from the groupconsisting of glasses, (fused) quartz, transmissive ceramic materials,and silicones. Also hybrid materials, comprising both inorganic andorganic parts may be applied. Especially, the light transmissivematerial comprises one or more of PMMA, transparent PC, or glass.

In yet another embodiment, the optical element may be configured tospecularly reflect the filament light. To this end, the facets may beprovided with specular mirrors, such as Al mirrors. In this way, theoptical element may be configured to redirect at least part of thefilament light (by specular reflection at the facets). For instance, inembodiments visible light propagating in a direction perpendicular tothe second axis of elongation may meet one or more facets, configuredsuch that visible light is reflected.

Hence, in embodiments the optical element is configured to redirect atleast part of the filament light by one or more of reflection at a facetand refraction at a facet. Hence, the optical element may have bothrefractive and reflective properties.

In yet other embodiments, the optical element may be configured todiffusively reflect the filament light. To this end, the facets maycomprise scattering structures, such as a white coating with roughnessselected to scatter the filament light. Alternatively or additionally,the optical element may comprise a light transparent material, with atthe facets and/or embedded in the body scattering features.

Scattering features at the facets may be roughness of the surface;scattering features in the body may be (scattering) particles, such ashaving particle sizes in the order of the wavelength of the light orlarger. Suitable transparent materials are indicated above; suitablescattering particles may be particles or bead or other shapes within abody of light transmissive material, wherein the scattering particleshave an index of refraction different from the light transmissivematerial. Such particles may thus comprise light reflective material,but may also comprise light transmissive material having an index ofrefraction different from the body of light transmissive material.Suitable reflective materials for reflection in the visible may beselected from the group consisting of TiO₂, BaSO₄, MgO, Al₂O₃, andTeflon. Herein, the term “diffuse reflective” may e.g. imply that underperpendicular radiation of a material that is diffuse reflective (or hasa diffuse reflective surface) with light, especially visible light, suchas white light or blue light, less than 20%, such as less than 10%, likein the range of 10-0.1%, even more especially in the range of 5-0.1%, oreven below 1%, may be specularly reflected. All other light that isreflected (at the surface or optionally in the bulk), is (essentially)diffusively reflected. Hence, in embodiments the optical element isconfigured to redirect at least part of the filament light by diffusereflection.

Combinations of above embodiments may also be possible, such inembodiments the optical element comprising parts, wherein for each partmay apply that the redirection of the filament light is based on atleast one of refraction, (specular) reflection, and scattering, andwherein in embodiments different parts may redirected filament light onthe basis of different principles (of these three principles).

In specific embodiments, the optical element may be configured toredirect at least 10% of the filament light. In yet further specificembodiments, the filament(s) and optical element are configured such,that equal to or less than 90% of the filament light is redirected.However, in other embodiments, all filament light may be redirected,e.g. to reduced glare. However, in yet other embodiments, the opticalelement (and filament(s)) is (are) configured to redirect in the rangeof 10-90%, such as 15-80%, of the filament light. In yet otherembodiments, the optical element (and filament(s)) is (are) configuredto redirect 15-45%, such as 20-40%, of the filament light.

In specific embodiments, the lighting device may comprise a plurality ofelongated filaments. Especially, in such embodiments the optical elementand the elongated filaments may be symmetrically arranged.

Especially, in embodiments the second axis of elongation may(essentially) coincide with an n-fold axis of rotation for n elongatedfilaments, like a three-fold rotation axis in the case of threefilaments, a four-fold rotation axis in the case of four filaments, etc.In embodiments, the second axis of elongation may be configured in oneor more mirror planes (of the filaments). Hence, in embodiments theoptical element is configured between at least two of the plurality ofelongated filaments.

In yet other embodiments, the elongated filament(s) comprises one ormore curves, and may circumfere the optical element.

In specific embodiments, the optical element has a non-circularcross-section perpendicular to the second axis of elongation.Especially, this may be useful for redirecting the filament light.Embodiments with a circular cross-section of the optical element appearto lead to more glare than embodiments of the optical element with anon-circular cross-section. Further, a sparkling effect may be weaker orabsent in the case of the circular cross-section, but (stronger) presentfor optical elements with a non-circular cross-section.

In embodiments, the optical element may have a cross-section(perpendicular to the second axis of elongation) having a shape selectedfrom the group of oval, triangle, square, rectangular, pentagonal,hexagonal, etc., such as up to about 24 facets, like up to about 12facets surrounded along the second axis of elongation.

In embodiments, the optical element may comprise 2-100 facets, such as2-50 facets, such as 2-20. In embodiments, the optical element maycomprises 3-12 facets, like 3-8 facets, such as 4-7 facets, like e.g. 5or 6 facets. However, much more, even over 100 facets, may also bepossible. Hence, in specific embodiments the optical element may have ata height along the first length 3-12 facets, i.e. the optical elementmay have a cross-section (perpendicular to the second axis ofelongation) having a 3-12 facets.

In embodiments, two or more facets of the optical element (unit) maycircumferentially surround the second axis of elongation. The facets maybe configured symmetrically around the second axis of elongation. Forinstance, the second facets may be configured such that one or moresymmetry planes are provided, wherein especially the second axis ofelongation is in the one or more symmetry planes.

The facets may thus be part of a hollow body or a massive body. Facetsat the same height may form a unit. The unit may be massive or hollow,such as a massive body of one or more the above-indicated lighttransmissive materials, or a hollow body comprising one or morereflective (and/or transmissive) faces.

The optical element may include a single unit, such as e.g. a hexagonalshaped cylinder or a regular tetrahedron. However, in embodiments theoptical element may comprise a stack of two or more of such units,herein also indicated as “optical element units”.

Hence, in embodiments the optical element may comprise one or moreoptical element units, wherein each optical element unit comprises oneor more of the plurality of facets. Especially, one or more of theoptical element units may be comprised by the optical element, whereinoptical element unit may comprise at least two facets, such as an oval(cross-section) with two facets, or three facets, such as a trigonalcylinder, or four facets, such as a regular pyramid, etc.

It further appears to be beneficial when the filament and closestfacet(s) may be configured such that e.g. not all possible mirror planesof symmetry for the facet (essentially) coincide with planes of symmetryof the filament(s).

For instance, the filament may be configured tilted relative to the(closest) facet(s). A tilt of the filament relative the facet mayinclude one or more of a tilt in a plane parallel to the facet and atilt in a plane perpendicular to the facet.

Alternatively or additionally, a normal to the facet may not intersectwith the filament. For instance, this may e.g. in specific embodimentsbe obtained when the filament is configured tilted relative to the facetor translated relative a normal to the facet.

Therefore, in embodiments for one or more of the facets of the opticalelement unit applies that a facet normal configured perpendicular to thefacet complies with one of the conditions selected from (i) the facetnormal does not intersect with an adjacent elongated filament, and (ii)the facet normal and the axis of elongation of an adjacent elongatedfilament have a mutual angle (β1) unequal to 90°.

The term “facet normal” especially refers to a normal to the facet at aposition of a centroid of the facet. A centroid of the facet is thearithmetic mean position of all the points in the facet. It can beconsidered the point at which a cutout of the shape could be perfectlybalanced on the tip of a pin.

As indicated above, the optical element may comprise a one or more ofthe optical element units. As also indicated above, a slanted elongatedfilament and/or a (differently) slanted facet (that reflects at leastpart of the filament light of the (slanted) elongated filament) may alsobe useful for improving the spatial distribution of the light. Forinstance, in embodiments the facet(s) of such unit may taper in adirection along the second axis of elongation. Hence, in specificembodiments the optical element may comprise one or more optical elementunits, wherein in specific embodiments one or more, especially eachoptical element unit, comprises one or more of the plurality of facets,wherein the one or more facets of the optical element unit areespecially symmetrically configured relative to the second axis ofelongation, and wherein in specific embodiments the one or more facetsof the optical element unit taper in a direction parallel to the axis ofelongation.

In embodiments, the optical element may comprise an ensemble of opticalelement units, which are stacked.

In embodiments the optical element comprises one or more optical elementunits, wherein each optical element unit comprises at least two facets,wherein the at least two facets are symmetrically configured relative tothe second axis of elongation, and wherein the facets taper in adirection parallel to the axis of elongation.

Further beneficial for the omni-directionality may be when two or moreoptical element units have different taper directions, especiallyopposite taper directions (along the second axis of elongation). Forinstance, two pyramids may be used, sharing a base. However, also astack of e.g. four or more tapering optical element units may be used.Therefore, in embodiments the lighting device may comprise one or moresets, wherein each set comprises two adjacently configured opticalelement units, wherein the optical element units within the set taper inopposite directions (along the second axis of elongation).

In embodiments, wherein the optical element units taper in oppositedirections, the shapes of the optical element units can be the same, andthus the taper may also be the same. However, the shapes of the opticalelement units (within a set) may also be different. In specificembodiments, the tapering may be different, such as the same type ofshapes for both the optical element units, but different taperings.Hence, in embodiments, the length of the optical element units along thesecond axis of elongation may differ for the two optical element units.When the length is shorter, the tapering is relatively stronger, andvice versa. When the tapering differs, in embodiments the surface areaof the top optical element unit, such as a pyramid, may in be largerthan the surface area of the bottom optical element unit, such as apyramid (or the other way around).

In a specific embodiment, a single set is applied, wherein in specificembodiments the tapering of the sets is in the direction of the ends ofthe optical element (e.g. the afore-mentioned two pyramids may be used,sharing a base). This may provide in embodiments that the facetsredirect filament light in a direction having a component parallel tothe second axis of elongation (more precisely, in two oppositedirections). Especially, in such embodiment, a tapering in the directionof a base (see also below), may be stronger, than a tapering in adirection of the other end of the lighting device (i.e. pointing awayfrom the base).

Two (or more) adjacent optical element units may form in embodiments asingle body. Alternatively, two adjacent optical element units may beprovided by two (different) bodies. Other embodiments may also bepossible. Hence, a single optical element may comprise a plurality ofoptical element units. More especially, a single optical element bodymay comprise a plurality of optical element units.

In yet other embodiments, the lighting device, especially the opticalelement, may comprise a plurality of the sets. The sets may be stacked.Hence, in embodiments the optical element comprises a stack of sets ofoptical element units. As indicated above, in embodiments the stack maybe a single body.

In specific embodiments, the first axes of elongation of the respectiveelongated filaments are configured parallel to the second axis ofelongation. In such embodiments, the filaments are configured parallelto the optical element (or at least its axis of elongation). Asindicated above, the filaments are especially configured symmetricallyrelative to the second axis of elongation.

In embodiments, the optical element comprises one or more opticalelement units, wherein each optical element unit comprises two or moreof the plurality of facets, wherein two or more of the two or morefacets circumferentially surround the second axis of elongation, whereinadjacent facets define a facet edge. In further specific embodiments,one or more filaments may be configured with their first axis ofelongation parallel to one or more of the facet edges. In yet furtherembodiments, one or more filaments are configured closest to arespective facet edge, and each facet (of the optical element unit) isconfigured at a larger distance from the respective filament than therespective facet edge. In such embodiments, a normal to a facet,especially to the centroid of the facets closest to the filament may notintersect the filament. As indicated above, in specific embodiments oneor more of the one or more optical element units each comprise 3-12facets. However, other embodiments of the number of facets are alsopossible (see e.g. above).

Therefore, in specific embodiments one or more of the facet edges, oneor more of the first axes of elongation, and the second axis ofelongation, are configured in a plane.

In (other) embodiments, as also indicated above, one or more of theplurality of first axes of elongation are slanted relative to the secondaxis of elongation. In yet further specific embodiments, the slanting ischosen such that the first axes of elongation of one or more of thefilaments are not in a same plane with the second axis of elongation.

In specific embodiments, one or more of the facets of the opticalelement are planar. In further specific embodiments, all facets of theoptical element are planar.

In (other) embodiments, one or more of the facets (of the opticalelement) are concave. In further specific embodiments, all facets of theoptical element are concave. The term “concave” indicates that the facetis hollow when viewed from the closest arrange filament and/or is convexwhen viewed from the second axis of elongation. With concave facets,filament light may also be redirected to improve omni-directionality ofthe filament light of the lighting device.

In (other embodiments), one or more of the facets (of the opticalelement) are convex. In further specific embodiments, all facets of theoptical element are convex.

In embodiments, parts of facets may be concave and other parts of (therespective) facets may be convex. Further, in embodiments wherein across-section with the optical elements shows that there are at leasttwo facets (i.e. not a single facet as may be the case when the opticalelement would have a circular cross-section), those facets may beconcave or convex. In specific embodiments, there may be one or morefacets, wherein each facet comprises a plurality of convex parts, or aplurality of concave parts, or one or more convex parts and one or moreconcave parts.

In embodiments (see also above), only one side of a filament may providefilament light. For instance, this may be used to reduce glare. Hence,in embodiments one or more of the plurality of elongated filaments isconfigured to provide more filament light in the direction of theoptical element than in opposite directions.

In embodiments, the spectral distribution of the filament lightgenerated at one side of the filament may be different from the filamentlight generated at the other side of the filament. This may be used forcreating specific effects. This may also be used to control the spectraldistribution of the lighting device light.

In embodiments, a configuration of a single optical element configuredbetween two or more filaments may be provided. In other embodiments, aconfiguration of a plurality of optical elements configured between twoor more filaments may be provided. In yet further embodiments, aplurality of sets is provided, wherein each set comprises a singleoptical element configured between two or more filaments.

In further embodiments, multiple optical elements may be provided thatmay be located around the central optical axis of the system (or withtheir center of gravity located on the central optical axis of thesystem). These two or more optical elements may be mounted parallel ormay make an angle (≠0° or ≠180°) with respect to each other.

As indicated above, with filaments a retro type of lamp may be provided,including a light transmissive bulb, and even when desired including apump stem. For instance, the optical element may be attached to the pumpstem.

Hence, the term “lighting device” may also refer to a lamp, especially alamp with a light transmissive bulb wherein the one or more filamentsand the optical element are configured.

The lighting device may have a lighting device axis or axis ofelongation. For instance, the outer shape of the lighting device mayessentially be symmetrical, with a rotational axis and/or one or moreplanes of symmetry, like many conventional light bulbs. In specificembodiments, the second axis of elongation may essentially coincide witha lighting device axis or axis of elongation.

In embodiments the lighting device may comprise (i) a base, and (ii) anouter bulb, together defining an enclosure enclosing the plurality ofelongated filaments and the optical element, wherein the solid statelight sources comprise LEDs, and wherein in specific embodiments theelongated filaments are straight elongated elements.

In embodiments, the optical element may further be configured to be asupport for the filaments. In embodiments, the optical element mayfurther be configured to enable feedthrough of one or more currentconductor(s) from the top end of the filament(s) back to the driver orsocket. The driver may be comprised by the base.

Especially, the lighting device is a retrofit lamp.

In embodiments, the lighting device may be included in or constitute aLED bulb or retrofit lamp which is connectable to a lamp or luminairesocket by way of some appropriate connector. For example an Edisonscrew, a bayonet fitting, or another type of connector suitable for thelamp or luminaire known in the art. The connector may be connected to abase portion, to which the elongated filament(s) and the optical elementmay be functionally coupled.

The lighting device may comprise a control system, such as e.g. at leastpartly comprised by the base. The control system may be configured tocontrol one or more of intensity of the filament light, intensity of thelight source light of individual light sources or sets of light sources,color point, color temperature, etc.

The term “controlling” and similar terms especially refer at least todetermining the behavior or supervising the running of an element.Hence, herein “controlling” and similar terms may e.g. refer to imposingbehavior to the element (determining the behavior or supervising therunning of an element), etc., such as e.g. measuring, displaying,actuating, opening, shifting, changing temperature, etc. Beyond that,the term “controlling” and similar terms may additionally includemonitoring. Hence, the term “controlling” and similar terms may includeimposing behavior on an element and also imposing behavior on an elementand monitoring the element. The controlling of the element can be donewith a control system, which may also be indicated as “controller”. Thecontrol system and the element may thus at least temporarily, orpermanently, functionally be coupled. The element may comprise thecontrol system. In embodiments, the control system and element may notbe physically coupled. Control can be done via wired and/or wirelesscontrol. The term “control system” may also refer to a plurality ofdifferent control systems, which especially are functionally coupled,and of which e.g. one control system may be a master control system andone or more others may be slave control systems. A control system maycomprise or may be functionally coupled to a user interface.

The control system may also be configured to receive and executeinstructions form a remote control. In embodiments, the control systemmay be controlled via an App on a device, such as a portable device,like a Smartphone or I-phone, a tablet, etc. The device is thus notnecessarily coupled to the lighting device, but may be (temporarily)functionally coupled to the lighting device.

Hence, in embodiments the control system may (also) be configured to becontrolled by an App on a remote device. In such embodiments the controlsystem of the lighting device may be a slave control system or controlin a slave mode. For instance, the lighting device may be identifiablewith a code, especially a unique code for the respective lightingdevice. The control system of the lighting device may be configured tobe controlled by an external control system which has access to thelighting device on the basis of knowledge (input by a user interface ofwith an optical sensor (e.g. QR code reader) of the (unique) code. Thelighting device may also comprise means for communicating with othersystems or devices, such as on the basis of Bluetooth, Wifi, ZigBee, BLEor WiMax, or another wireless technology.

Hence, in embodiments, the control system may control in dependence ofone or more of an input signal of a user interface, a sensor signal (ofa sensor), and a timer. The term “timer” may refer to a clock and/or apredetermined time scheme.

The lighting device may be part of or may be applied in e.g. officelighting systems, household application systems, shop lighting systems,home lighting systems, accent lighting systems, spot lighting systems,theater lighting systems, fiber-optics application systems, projectionsystems, self-lit display systems, pixelated display systems, segmenteddisplay systems, warning sign systems, medical lighting applicationsystems, indicator sign systems, decorative lighting systems, portablesystems, automotive applications, (outdoor) road lighting systems, urbanlighting systems, green house lighting systems, horticulture lighting,etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIGS. 1a-1b schematically depicts a retrofit lamp, without an opticalelement, and an associated intensity distribution;

FIGS. 2a-2b schematically depicts an embodiment of such retrofit lampwith an optical element, and an associated intensity distribution;

FIGS. 3a-3b schematically depicts an embodiment of such retrofit lampwith an another embodiment of the optical element, and an associatedintensity distribution;

FIGS. 4a-4b schematically depicts an embodiment of such retrofit lampwith an another embodiment of the optical element, and an associatedintensity distribution;

FIGS. 5a-5b schematically depicts an embodiment of such retrofit lampwith an another embodiment of the optical element, and an associatedintensity distribution;

FIGS. 6a-6b schematically depicts an embodiment of such retrofit lampwith an another embodiment of the optical element, and an associatedintensity distribution;

FIG. 7a schematically depicts an embodiment of a retrofit lam and anoptical element;

FIG. 7b schematically depicts a plurality of filament and opticalelement configuration;

FIG. 8a schematically depicts another embodiment of a retrofit lam andan optical element;

FIG. 8b schematically depicts a plurality of filament and opticalelement configuration;

FIGS. 9a-9b schematically depict some further embodiments;

FIGS. 10a-10c schematically depict some further embodiments; and

FIGS. 11a-11b schematically depict filament embodiments.

The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It appears appreciated and desired by users to have a retrofit lampwhich has the look of an incandescent bulb. For this purpose, one cansimply make use of the infrastructure for producing incandescent lampsbased on glass and replace the filament with LEDs emitting white light.

One of the concepts is based on LED filaments placed in such a bulb. Theappearances of these lamps are highly appreciated as they look highlydecorative. FIGS. 1a-1b schematically depicts a retrofit lamp, withoutan optical element, and an associated intensity distribution. However,such solution may not provide omnidirectional light distribution. FIG. 1b shows that there is (almost) no light is going up and downwards(downward light is also partly screened by lamp base.)

Amongst others, a LED lamp comprising one or more, especially aplurality, such as at least three LED filaments (i.e. a linear array ofLEDs on an elongated substrate preferably encapsulated by a luminescentmaterial) adapted for, in operation, emitting LED filament light isherein suggested. The LED filaments may be arranged in an at leastpartly transparent envelope. The light emitting surface of the LEDfilaments are especially oriented towards a distantly arrangedreflective (or refractive) element which is centrally arranged in theenvelope. In embodiments, the LED filaments are evenly arranged aroundthe reflective element. The reflective element may in embodiments havereflective surfaces for reflecting light in other directions forobtaining omnidirectional distribution.

In embodiments, the reflective element may be cone-shaped. In specificembodiments, the reflective element may have a double cone shape (twocone configuration). For instance, in specific embodiments thereflective element may have a double pyramid shape (two pyramidconfiguration). The surface area of the top pyramid may in embodimentsbe larger than the surface area of the bottom pyramid.

In further specific embodiments, the LED filament may be chosen to emitlight from only one surface facing the reflector preventing glare. Theother surface may be covered by a layer (other than a phosphor), e.g. ablack/metal coating, for instance to give the filament the appearance ofan incandescent lamp. Further, amongst others (also) a segmentedreflector in the center of the lamp is herein suggested, with thefilaments mounted around this reflector. This reflector may also act assupport for the filaments and may enable feedthrough of the currentconductor(s) from the top end of the filaments back to the driver orsocket.

FIG. 1a shows an embodiment of a lighting device 10 (but without opticalelement) comprising (i) a base 14, and (ii) an outer bulb 13. The outerbulb together with the base may define an enclosure 113 enclosing theplurality of elongated filaments 100 and the optical element (notdepicted). Here, in this schematically depicted embodiment the elongatedfilaments 100 are straight elongated elements 100. The lighting device10 has a device axis or (device) axis of elongation 15. The device 10 isessentially rotationally symmetry around this axis 15 and/or comprisesone or more (here in fact a plurality) of symmetry planes, which eachcomprise the device axis of elongation 15. Reference 16 indicates anoptional pump stem. The same device 10 without outer bulb 13 is depictedat the right side of FIG. 1 a.

FIG. 1a is further explained below after a short introduction of FIG. 2a. FIG. 1b shows the intensity distribution. As shown, upwards anddownwards, the intensity is relatively low. The intensity distributionhas a kind of donut shape.

FIGS. 2a-2b schematically depicts an embodiment of such retrofit lampwith an optical element, and an associated intensity distribution. Here,the optical element has a pyramid shape.

FIGS. 1a and 2a schematically depict several aspects of embodiments ofthe invention. In FIG. 1a , a lighting device 10 is schematicallydepicted comprising a plurality of elongated filaments 100. FIG. 1bschematically depicts an embodiment of the elongated filaments and anoptical element 200.

Each elongated filament 100 comprises a substrate or support (see FIGS.11a-11b ) and a plurality of solid state light sources configured togenerate solid state light source light.

The elongated filament 100 has a first axis of elongation 120 having afirst length L1. The elongated filament 100 is configured to generatefilament light 101 over at least part of the first length L1.

The optical element 200 comprises a plurality of facets 210. Especially,adjacent facets 210 have mutual facet angles (unequal to 0°). Theoptical element 200 has a second axis of elongation 220 having a secondlength L2. Especially, the optical element 200 has a non-circularcross-section perpendicular to the second axis of elongation 220. Here,the optical element 200 comprises a single optical element unit 1200(which both have a length L2).

The optical element 200 is configured between at least two of theplurality of elongated filaments 100. The optical element 200 isconfigured to redirect at least part of the filament light 101.

FIG. 2a also shows an embodiment wherein the optical element 200comprises one or more optical element units 1200 (here one opticalelement unit 1200). The optical element unit 1200 comprises one or moreof the plurality of facets 210. Especially, for one or more of thefacets 210 of the optical element unit 1200 applies that a facet normal211 configured perpendicular to the facet 211 complies with one of theconditions selected from (i) the facet normal 211 does not intersectwith an adjacent elongated filament 100 (this may however be the case inthe embodiment of FIG. 2a ; see therefore also e.g. FIG. 7b ,configurations X-XII), and (ii) the facet normal 211 and the axis ofelongation 220 of an adjacent elongated filament 100 have a mutual angleβ1 unequal to 90°, such as in the schematically depicted embodiments ofe.g. FIGS. 2a, 3a, 4a, 5a , etc.

In this (and other) embodiment(s), the one or more facets 210 of theoptical element unit 1200 are symmetrically configured relative to thesecond axis of elongation 220. Further, as schematically depicted ine.g. FIGS. 2a, 3a, 4a, 5a , etc. the one or more facets 210 of theoptical element unit 1200 taper in a direction parallel to the axis ofelongation 220.

FIG. 2a (but also e.g. FIG. 3a , FIG. 4a , FIG. 5a , etc.) also shows anembodiment, wherein the first axes of elongation 120 of the respectiveelongated filaments 100 are configured parallel to the second axis ofelongation 220.

Further, FIG. 2a also shows an embodiment wherein the optical elementunit 1200 comprises two or more of the plurality of facets 210, whereintwo or more of the two or more facets 210 circumferentially surround thesecond axis of elongation 220, wherein adjacent facets 210 define afacet edge 212. Further, as schematically depicted one or more of theone or more optical element units 1200 each comprise 3-12 facets 210. Ine.g. FIGS. 2a and 3a , the optical elements 200/optical element units1200 comprise 4 facets (not taking into account the bottom facet).

Especially, the reflective or refractive element may have a doublepyramid shape i.e. two pyramid configuration. FIGS. 3a-3b schematicallydepicts an embodiment of such retrofit lamp with another embodiment ofthe optical element, and an associated intensity distribution (for thelamp, see FIG. 1a ; here, only the relevant elements of the filamentsand the optical element are schematically depicted).

FIGS. 3a (and 4 a) shows an embodiment(s) one or more sets 1230 (here asingle set), wherein the set 1230 comprises two adjacently configuredoptical element units 1200, wherein the optical element units 1200within the set 1230 taper in opposite directions. The surface area ofthe top pyramid may be larger than the surface area of the bottompyramid.

It appears that a faceted pyramid shaped reflector element outperforms acone shaped design (i.e. round reflector as shown in FIGS. 4a-4b )because more light is redirected. FIGS. 4a-4b schematically depicts anembodiment of such retrofit lamp with another embodiment of the opticalelement, and an associated intensity distribution (again: for the lamp,see FIG. 1a ; here, only the relevant elements of the filaments and theoptical element are schematically depicted).

The design principle described above also hold for a refractive element.In other words, the refractive element is preferably faceted. Forexample, a refractive pyramid may be used. FIGS. 5a-5b schematicallydepicts an embodiment of such retrofit lamp with another embodiment ofthe optical element, and an associated intensity distribution (again:for the lamp, see FIG. 1a ; here, only the relevant elements of thefilaments and the optical element are schematically depicted).

In another example a cube comprising a reflective/refractive pyramidcavity can be used. FIGS. 6a-6b schematically depicts an embodiment ofsuch retrofit lamp with another embodiment of the optical element, andan associated intensity distribution (again: for the lamp, see FIG. 1a ;here, only the relevant elements of the filaments and the opticalelement are schematically depicted).

FIGS. 7a-10c schematically depict some further embodiments.

FIG. 7a schematically depicts an embodiment of a retrofit lam and anoptical element. FIG. 7a shows an embodiment of a basic LED filamentbulb configuration with a centrally mounted optical element (such as areflector). This embodiment includes configuration I with an elongatedsquare reflector. FIG. 7b schematically depicts a plurality of filamentsand optical element configuration (which may e.g. be applied in theembodiment of FIG. 7a ). Configuration (II) shows an elongated hexagonalreflector, and configuration (II) shows a cylindrical reflector.

As an example, essentially all versions are shown here with fourfilaments.

To prevent reflection of light straight back onto the filament, as wellas with the purpose to see multiple virtual sources, it may beadvantageous to not let the normal of the reflector segment(essentially) coincide with the position of a filament. This results inpreferred orientations of the centrally mounted segmented reflector, asshown for some basic configurations in FIG. 7b configurations IV-VI.Here, a centrally mounted reflector where the reflector segment normalsare non-coinciding with the filament positions are schematicallydepicted. Configuration IV shows an elongated square reflector,configuration V shows an elongated hexagonal reflector, andconfiguration VI shows an elongated octagonal reflector.

In the embodiments of configurations IV-VI one or more of the facetedges 212, one or more of the first axes of elongation and the secondaxis of elongation, are configured in a plane.

In this set of configurations, all versions IV through VI) show alay-out where all segment normals do not (essentially) coincide with thefilament positions. In this example this was realized by using aninteger multiplier of 1 (for configuration IV) or 2 (for V and VI) asthe relation between the number of filaments and the number of segments,and although this results in nicely symmetrical configurations, thisdoes not necessarily have to be the case.

The reflector segments would not necessarily need to be flat. It mayeven be advantageous to use concave or convex segments as this enableseither a more homogeneous (local) distribution of brightness, or enablespreventing occurrence of perceived increased brightness as it shows thevirtual (reflected) sources at larger distances from the direct-viewsource. Some basic embodiments with concave reflector segments are shownin FIG. 7b configurations VII-IX. Here, embodiments with centrallymounted reflectors with concave reflector segments are schematicallydepicted. Configuration VII shows an elongated 4-segment concavereflector where the segment normal are coinciding with the filamentpositions, configuration VIII shows an elongated 4-segment concavereflector where the segment normals do not (essentially) coincide withthe filament positions, and configuration IX shows an elongatedhexagonal concave reflector (having by way of example a combination ofcoinciding and non-coinciding configurations of filament and reflectornormals). As an example, essentially all versions are shown here with 4filaments. Hence, here embodiments are schematically depicted whereinone or more of the facets 210 are concave. In an alternative embodimentof configuration VII of FIG. 7B, the reflector segments partiallysurround the filaments 100, i.e. at least a part of the filament 100 ispositioned in a virtual space defined by the surface of the facet 210and a plane bounded by two opposing facet edges 212 of that facet 210.Alternatively, the filament 100 is completely positioned in a virtualspace defined by the facet 210 and a plane bounded by two opposing facetedges 212 of that facet 210. The optical element 200 may be transparent.An advantage of this configuration is that the uniformness of theillumination pattern in the far field is further improved. In case of atransparent optical element 200, the filaments are still visible fromall viewing angles.

The examples shown above used in most cases just four filaments, but ofcourse extension of the number of filaments to a lower or higher countare possible. A configuration with 3 filaments was already shown inconfiguration V. As an example, configurations X-XII show some basicembodiments for the extension from 4 to 6 and 8 filaments in combinationwith respective a square, a hexagonal, and an octagonal centralreflector. Hence, configurations with a centrally mounted reflector withincreasing number of filaments. Configuration X shows an elongated4-segment reflector where the segment normals are not coinciding withthe filament positions, configuration XI shows an elongated 6-segmentreflector where the segment normals do not (essentially) coincide withthe six filament positions, and configuration XII shows an elongatedoctagonal reflector, where the segment normals do not (essentially)coincide with the eight filament positions.

In most of the above examples, the number of filaments and the number ofreflector segments were chosen equal, but of course also other ratioscan be used, such as four filaments with an octagonal reflector.

So far, the filaments were depicted all in parallel with the elongationdirection of the centrally mounted reflector. However, it may bebeneficial to tilt the filaments such that as a function of height theorientation towards, or position relative to, the reflector varies,resulting in a more diverse brightness distribution of the (virtual)sources. This is shown for some basic configurations in FIGS. 8a-8b .Here, configurations are depicted with a centrally mounted reflector,where the filaments are tilted in the tangential planes around thereflector. Configurations I, II, and III show respective configurationswith a hexagonal (6 segment), a square (4 segment), and an octagonal (8segment) reflector. All versions are shown here with 4 filaments as anexample. FIG. 8a schematically depicts another embodiment of a retrofitlam and an optical element. Here, one or more of the plurality of firstaxes of elongation 120 are slanted relative to the second axis ofelongation 220. FIG. 8b schematically depicts a plurality of filamentand optical element configuration (that may e.g. be used in theembodiment of FIG. 8a ).

As a further extension of meaningful orientations of the filaments, theymay be tilted radially inwards or outwards with respect to the opticalaxis of the lamp or central reflector. The same holds for the averageorientation of the reflector surfaces; also these may be tilted inwardsor outwards with respect to the optical axis of the system. Inparticular for beam profile adjustments this can be meaningful, as therelative flux emitted in the longitudinal direction compared to thatemitted radially is impacted by this. Some basic configurations arepresented in FIGS. 9a-9b , which schematically depict some furtherembodiments. LED filament bulb configurations are schematically depictedwith a centrally mounted reflector, where the filaments and/or thereflector segments are tilted in the radial direction with respect tothe optical axis of the system. The configuration in FIG. 9a shows anoctagonal cylindrical reflector with filaments that are tilted in boththe tangential planes and in the radial planes. The configuration inFIG. 9b shows and octagonal reflector with radially tilted segments,combined with filaments that are tilted in both the tangential planesand in the radial planes. All versions are shown here with 4 filamentsas an example. Of course the upside-down version of the configuration inFIG. 9b is possible and relevant as well.

The reflector may, in alternative embodiments, be composed of segmentsthat not only show variation in the direction of the surface normal as afunction of the circumferential position, but also as a function of theheight position. This enhances further sparkle effects and may be usedas well for further beam shape optimization. Some examples are shown inFIGS. 10a-10c , which schematically depict some further embodiments.These figures schematically depicted also embodiments of LED filamentbulb configurations with a centrally mounted reflector, where thereflector segments are tilted locally. The configurations of FIGS. 10and 10 b show a layered reflector configuration, while the configurationof FIG. 10c shows a spiraling reflector configuration. As an example,all versions are shown here with a square basic outline of the reflectorand with 4 filaments.

Special effects may also be achieved by using a partiallytransparent/translucent and partly reflective central reflectorstructure. The reflection characteristics may be substantially specular.In other embodiments, however, the reflective layer may be spreading thebeam substantially, as may be achieved by small curved surface elementssuch as a reflective granular surface structure.

It is obvious that many combinations of the aforementionedimplementation options are possible with respect to the number offacets, number of filaments, orientation of the facets, orientation ofthe filaments, and optical nature of the reflector surface and the bodyof the reflector.

A general aspect of at least some of the embodiments shown is that oneor more electrical leads is guided through the center of the reflector,but this is not necessarily the case; also electrical leads going backfrom the top of the filaments to the base of the lamp outside thecentral reflector are possible.

The examples shown here indicate that the various filaments areconnected in parallel at their top, but of course they can be mounted asindividually addressable or in series as well.

Filaments may be emitting substantially the same spectral content, butmay also be configured to emit different spectral content. In particularfor dynamic sparkling with multi-facetted centrally mounted reflectorsin may be attractive to use different color points for some of thefilaments.

FIGS. 11a-11b schematically depict an embodiment of an elongatedfilament 100. The elongated filament 100 has a first length L1 alongwhich light source light 11 is generated. Here, the elongated filament100 comprises a plurality of solid state light sources 110, which areconfigured along the first length L1 and configured to generate solidstate light source light 111.

In embodiments, the light source light 11 may essentially consist of thesolid state light source light. In other embodiments, such as furtherdescribed below, the light source light may comprise luminescentmaterial light 151, which is based on an at least partial conversion ofthe solid state light source light 111 into luminescent material light151 by a luminescent material 150. In yet further embodiments, the lightsource light may comprise luminescent material light 151 and solid statelight source light 111.

The solid state light sources 110 may be available on a substrate 105.Further, the solid state light sources 110 (and the substrate 105) mayespecially be embedded in a light transmissive material (in generaldifferent from the light transmissive material of the light guideelement), such as a resin. The light transmissive material enclosing thelight sources is indicated with reference 145. Especially, the lighttransmissive material may comprise, such as embed, a luminescentmaterial 150. Especially, this light transmissive material 145 may be aresin comprising luminescent material 150, such as an inorganicluminescent material in an organic resin. The resin may e.g. an acrylateor a silicone resin or an epoxy resin, etc.

Due to the fact that the light transmissive material 145 encloses thesolid state light sources 110 and the substrate 105, light that isgenerated within the light transmissive material 145 may radiate inessentially any direction (perpendicular to an axis of elongation 110).This is also shown in the cross-sectional view in FIG. 11b . Hence, theelongated filament 100 in embodiments the elongated filament 100 isconfigured to provide light source light 11 in a plurality of directionsperpendicular to the axis of elongation 120.

Hence, FIGS. 11a-11b schematically depict an embodiment of the elongatedfilament 100, wherein the elongated filament 100 comprises, wherein theelongated filament 100 comprises luminescent material 150 configured toconvert at least part of the solid state light source light 111 intoluminescent material light 151, and wherein the light source light 11comprises the luminescent material light 151 and optionally solid statelight source light 111. Reference 105 indicates a support or substrate.

As schematically depicted in FIGS. 11a and 11b with the dashed line,light source light 111 is generated over essentially 360° around theaxis of elongation 110 (see FIG. 11b ). With reference to FIG. 11a ,relative to the axis of elongation 110 segments or a kind of elongatedsemi-circles, or a kind of elongated circles, can be defined, in whichalso light source light is generated over essentially 180° or 360°,respectively, see FIG. 11 a.

The term “plurality” refers to two or more.

The terms “substantially” or “essentially” herein, and similar terms,will be understood by the person skilled in the art. The terms“substantially” or “essentially” may also include embodiments with“entirely”, “completely”, “all”, etc. Hence, in embodiments theadjective substantially or essentially may also be removed. Whereapplicable, the term “substantially” or the term “essentially” may alsorelate to 90% or higher, such as 95% or higher, especially 99% orhigher, even more especially 99.5% or higher, including 100%.

The term “comprise” includes also embodiments wherein the term“comprises” means “consists of”.

The term “and/or” especially relates to one or more of the itemsmentioned before and after “and/or”. For instance, a phrase “item 1and/or item 2” and similar phrases may relate to one or more of item 1and item 2. The term “comprising” may in an embodiment refer to“consisting of” but may in another embodiment also refer to “containingat least the defined species and optionally one or more other species”.

Furthermore, the terms first, second, third and the like in thedescription and in the claims, are used for distinguishing betweensimilar elements and not necessarily for describing a sequential orchronological order. It is to be understood that the terms so used areinterchangeable under appropriate circumstances and that the embodimentsof the invention described herein are capable of operation in othersequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others bedescribed during operation. As will be clear to the person skilled inthe art, the invention is not limited to methods of operation, ordevices, apparatus, or systems in operation.

It should be noted that the above-mentioned embodiments illustraterather than limit the invention, and that those skilled in the art willbe able to design many alternative embodiments without departing fromthe scope of the appended claims.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim.

Use of the verb “to comprise” and its conjugations does not exclude thepresence of elements or steps other than those stated in a claim. Unlessthe context clearly requires otherwise, throughout the description andthe claims, the words “comprise”, “comprising”, and the like are to beconstrued in an inclusive sense as opposed to an exclusive or exhaustivesense; that is to say, in the sense of “including, but not limited to”.

The article “a” or “an” preceding an element does not exclude thepresence of a plurality of such elements.

The invention may be implemented by means of hardware comprising severaldistinct elements, and by means of a suitably programmed computer. In adevice claim, or an apparatus claim, or a system claim, enumeratingseveral means, several of these means may be embodied by one and thesame item of hardware. The mere fact that certain measures are recitedin mutually different dependent claims does not indicate that acombination of these measures cannot be used to advantage.

The invention also provides a control system that may control thedevice, apparatus, or system, or that may execute the herein describedmethod or process. Yet further, the invention also provides a computerprogram product, when running on a computer which is functionallycoupled to or comprised by the device, apparatus, or system, controlsone or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or systemcomprising one or more of the characterizing features described in thedescription and/or shown in the attached drawings. The invention furtherpertains to a method or process comprising one or more of thecharacterizing features described in the description and/or shown in theattached drawings.

The various aspects discussed in this patent can be combined in order toprovide additional advantages. Further, the person skilled in the artwill understand that embodiments can be combined, and that also morethan two embodiments can be combined. Furthermore, some of the featurescan form the basis for one or more divisional applications.

The invention claimed is:
 1. A lighting device comprising (i) aplurality of elongated filaments and (ii) an optical element, wherein:each elongated filament comprises a support and a plurality of solidstate light sources, wherein the elongated filament has a first axis ofelongation having a first length, wherein the elongated filament isconfigured to generate filament light over at least part of the firstlength; and the optical element comprises a plurality of facets, whereinthe optical element has a second axis of elongation having a secondlength, wherein the optical element has a non-circular cross-sectionperpendicular to the second axis of elongation, wherein the opticalelement is configured between at least two of the plurality of elongatedfilaments, and wherein the optical element is configured to redirect atleast part of the filament light, wherein the optical element comprisesone or more optical element units, wherein each optical element unitcomprises one or more of the plurality of facets, wherein the one ormore facets of the optical element unit are symmetrically configuredrelative to the second axis of elongation, and wherein the one or morefacets of the optical element unit taper in a direction parallel to theaxis of elongation and, the lighting device further comprising one ormore sets, wherein each set comprises two adjacently configured opticalelement units, wherein the optical element units within the set taper inopposite directions.
 2. The lighting device according to claim 1,wherein the optical element is configured to redirect at least part ofthe filament light by one or more of reflection at a facet andrefraction at facets.
 3. The lighting device according to claim 1,wherein the optical element is configured to redirect at least part ofthe filament light by diffuse reflection.
 4. The lighting deviceaccording to claim 1, wherein the optical element comprises one or moreoptical element units, wherein each optical element unit comprises oneor more of the plurality of facets, wherein for one or more of thefacets of the optical element unit applies that a facet normalconfigured perpendicular to the facet complies with one of theconditions selected from (i) the facet normal does not intersect with anadjacent elongated filament, and (ii) the facet normal and the axis ofelongation of an adjacent elongated filament have a mutual angle (β1)unequal to 90°.
 5. The lighting device according to claim 4, wherein thefirst axes of elongation of the respective elongated filaments areconfigured parallel to the second axis of elongation.
 6. The lightingdevice according to claim 1, wherein the elongated filament comprisesluminescent material configured to convert at least part of the solidstate light source light into luminescent material light, and whereinthe filament light comprises the luminescent material light andoptionally the solid state light source light.
 7. The lighting deviceaccording to claim 6, wherein the filament light is generatedessentially 360° around the axis of elongation.
 8. The lighting deviceaccording to claim 6, comprising a plurality of the sets.
 9. Thelighting device according to claim 1, wherein the optical elementcomprises one or more optical element units, wherein each opticalelement unit comprises two or more of the plurality of facets, whereintwo or more of the two or more facets circumferentially surround thesecond axis of elongation, wherein adjacent facets define a facet edge.10. The lighting device according to claim 9, wherein one or more of theone or more optical element units each comprise 3-12 facets.
 11. Thelighting device according to claim 9, wherein one or more of the facetedges, one or more of the first axes of elongation, and the second axisof elongation, are configured in a plane.
 12. The lighting deviceaccording to claim 1, wherein one or more of the plurality of first axesof elongation are slanted relative to the second axis of elongation. 13.The lighting device according to claim 1, wherein one or more of thefacets are concave.
 14. The lighting device according to claim 1,wherein one or more of the plurality of elongated filaments isconfigured to provide more filament light in the direction of theoptical element than in opposite directions.
 15. The lighting deviceaccording to claim 1, comprising (i) a base, and (ii) an outer bulb,together defining an enclosure enclosing the plurality of elongatedfilaments and the optical element, wherein the solid state light sourcescomprise LEDs, and wherein the elongated filaments are straightelongated elements.